The effects of salicylates on phenomena related to crown gall

The effects of acetylsalicylate and salicylate were investigated on three phenomena involved in crown-gall disease. First, an inhibition of the growth of Agrobacterium tumefaciens was observed with low concentrations of salicylates. This inhibition was pH dependent and was partially reversed by glutamate. Second, an inhibition of the growth of tobacco tumor tissue was observed only at high concentrations of salicylates. Third, tumor formation on excised tobacco leaves was inhibited by low concentrations of salicylates. The inhibition of tumor formation occurred at salicylate concentrations that had no significant effect on the net rate of photosynthesis by the leaves. The inhibition of tumor formation was also observed with a mutant strain of A. tumefaciens resistant to salicylate. The potential interest of salicylates as control agents for crown-gall disease is discussed.